I'm sure this has been asked, and I'm sure I've read this here someplace, but I've been searching all morning....
What wires are better to extend if I have to? The wires going to the speed controller, or the wires going to the motor, I've seen it done both ways (I Think), and just though I would ask the EXPERTS on this great forum!!

The setup I am referring to is a new build I'm working on, I just unpacked the new Turnigy H.A.L Hex (love it BTW) and thought about ESC placement. I saw in the HAL thread, a bunch of pics showing the ESC's mounted inside the dome with the wires extended from there, My issue with that is I feel there is not enough cooling for them???
So I want put mine on the arms and extend from my power board, the opposite way.
Is there and benefit to either way?

I purchased a spare H.A.L quad bottom plate, I plan to mount the spare bottom plate spaced away from the existing bottom plate and mount the landing gear on it, ESC placed between the 2 bottom plates and are not covered by the dome. Purchased spare screw pack and some nylon spacers. That way the extended wiring from ESC to motor can go neatly inside the arms and airflow to ESC is not restricted by the dome.

You want the cable from Lipo to ESC as short as possible, You want that wiring and the whole power distribution to be as far away from the magnetometer as possible.

You do not want to mount the ESCs surrounding the FC inside the dome as a LOT of people seem to do. That is simply wrong.

Reasons; the wiring from Lipo to ESC carries heavy currents which creates strong varying magnetic fields and will be right under, very close to the magnetometer making the magnetometer/Compass useless AND WORSE if you fly headfree the frame will yaw violently when you apply throttle to lift off as the magnetometer is severely affected by the strong magentic field around the Lipo to ESC wiring right underneath it.

The ESC cannot really tolerate long wires to Lipo, the capacitor on ESC will get hotter, will fail sooner, generally you will have more electrical noise.
Aim for ALL of these;
Keeping Lipo to ESC wiring as far away as possible from Flight Controller magnetometer,

I purchased a spare H.A.L quad bottom plate, I plan to mount the spare bottom plate spaced away from the existing bottom plate and mount the landing gear on it, ESC placed between the 2 bottom plates and are not covered by the dome. Purchased spare screw pack and some nylon spacers. That way the extended wiring from ESC to motor can go neatly inside the arms and airflow to ESC is not restricted by the dome.

You want the cable from Lipo to ESC as short as possible, You want that wiring and the whole power distribution to be as far away from the magnetometer as possible.

You do not want to mount the ESCs surrounding the FC inside the dome as a LOT of people seem to do. That is simply wrong.

Reasons; the wiring from Lipo to ESC carries heavy currents which creates strong varying magnetic fields and will be right under, very close to the magnetometer making the magnetometer/Compass useless AND WORSE if you fly headfree the frame will yaw violently when you apply throttle to lift off as the magnetometer is severely affected by the strong magentic field around the Lipo to ESC wiring right underneath it.

The ESC cannot really tolerate long wires to Lipo, the capacitor on ESC will get hotter, will fail sooner, generally you will have more electrical noise.
Aim for ALL of these;
Keeping Lipo to ESC wiring as far away as possible from Flight Controller magnetometer,

keeping Lipo to ESC wires as short as possible,

Extend the wires from ESC to motor

Do not restrict cooling airflow around ESC.

So even if I say mount them on the arms, just on the outside of the dome, thats better than having them right under the dome, with all the noise just bouncing around in there messing things up??

That way I wont have to extend the wires from the lipo, just going to the motors.

So even if I say mount them on the arms, just on the outside of the dome, thats better than having them right under the dome, with all the noise just bouncing around in there messing things up??

That way I wont have to extend the wires from the lipo, just going to the motors.

I like your idea of the extra plate for mounting things on.....

Mounting them on the arms is what I did on the HK Talon, BUT I also had to raise the flight controller so as to keep it away the strong magnetic field generated by the wires between the lipo and ESC when the motors are running, the electrical noise generated by the ESC is not as bad as the magnetic field from the Lipo cables affecting the Magnetometer/Compass

Yeah, buying a spare bottom plate which I am waiting for delivery is a lot easier and should end up a lot neater looking, gets around the problem of not having lots of nice clear space for ESC and power distribution without adding too much weight.

By the way you do NOT extend the wires from ESC to lipo they are already long enough to reach your power distribution arrangement even if you mount the ESC on the arms.

You want the cable from Lipo to ESC as short as possible, You want that wiring and the whole power distribution to be as far away from the magnetometer as possible.

Reasons; the wiring from Lipo to ESC carries heavy currents which creates strong varying magnetic fields and will be right under, very close to the magnetometer making the magnetometer/Compass useless AND WORSE if you fly headfree the frame will yaw violently when you apply throttle to lift off as the magnetometer is severely affected by the strong magentic field around the Lipo to ESC wiring right underneath it.

The ESC cannot really tolerate long wires to Lipo, the capacitor on ESC will get hotter, will fail sooner, generally you will have more electrical noise.

Sorry, don't take it personally, but most of this is incorrect.. and anyone who know electronics will confirm...
Magnetic field is generated when current is being switched on/off thru wire - the wires from ESC to motor are the ones which are used for switching the power (only 2 wires from the 3 motor wires are used at once).

Therefore, those wires are the one which generates electro-magnetic field. If you make those wires longer, the bigger the field will be. Also long wires may attenuate the back EMF from motor to ESC (which is used for sensing the motor position) and it may cause misfires (cracking noise in motor).

The wires from ESC to battery are always at the same voltage and not being turned off. Only the current is changing, but the changes are not as fast - the capacitor at the ESC is supposed to help with that.

And the last point is the weight - mounting the ESC close to the motor you have to prolong only 2 wires and not 3. (+1 thin wire for signal)

Not quite right either! A magnetic field is generated when a current flows in a conductor, so that includes the DC current from the battery. You might be thinking of a varying magnetic field inducing a current in a conductor (as in a transformer secondary or a generator).

Depending on the magnetometer frequency response, the field from the DC supply may cause more problems than the rapidly varying field from the motor wires.

The consensus (based on recommendations from some manufacturers) seems to be that it's better to extend the ESC-to-motor wires rather than the ESC-to-battery wires... whether it really matters I don't know.

Per the right-hand rule it doesn't matter if the current is being switched. It will still generate a magnetic field. If the direction of current is changing, the magnetic field's poles will change. The direction of current from the ESC to the motor changes to make the motor turn, so the field would be constantly switching.

As such, both the wires from the battery to ESC, and the wires from the ESC to motor will generate a magnetic field. The higher the current, the stronger the magnetic field.

If you keep your battery negative and positive wires close together (parallel) and don't have any large loops, then the magnetic fields created by each wire will tend to cancel and shouldn't affect compass/magnetometer too much. Likewise, keep the 3 wires from ESC to motor bundled together and there will be less stray magnetic field.

mattcro: you're right, I forgot about static magnetic field (which certainly is generated by DC flow) as a static magnetic field wouldn't cause any inducted electricity and shouldn't therefore create inducted noise... however the magnetic field will be still present and magnetometer will be either way affected...
So the only option is to keep the magnetometer far away...

Practical testing of the various theories in the actual application beats selectively applying theories and mixing it with lots of guesswork.

Take a spare flight controller with a magnetometer and Magnetic Compass display, observe the influence on the Magenitc Compass while you move that flight controller [magnetometer] at varying [PRACTICAL] distances around all the wiring from lipo to motor on another frame with props mounted and sufficient throttle to achieve hover applied.

What do you see, tell us all your actual findings.

My post was made AFTER I had actually performed extensive testing, not based on guesswork at all as assumed by some here.

By the way, I did order a spare bottom plate, ended up not using it, instead raised the H.A.L Quad undercarriage and placed the ESC under the existing bottom plate, photos below, Magnetic Compass is deflected 3 degrees from motors disarmed to motors way above hover 1100KV motors on 4s Lipo 30A ESC [Modified] with 9x4.7 props